The present invention pertains to foamable compositions that, on foamed release thereof from an aerosol canister or the like, present a stable foamed product capable of use as a caulk, sealant, or insulating compound.
Caulking, insulation and sealant compositions are used to seal joints and other voids and to reinforce framing, tiles, panels, lathing, wall board and other structural assemblies. Foamed application of such compositions from pressurized containers and the like is highly desirable due primarily to overall ease of application. Easy clean up concerns require that such foamed products should be washed off with simple soap and water solutions.
Some of the available foamed compositions are not stable and shrink after foamed application to the desired structure. Quite obviously, these products therefore fail in providing overall sealing or insulating efficacy. Moreover, other foamed products tend to sag or drip after application, again leading to failure.
Also, foams are often applied during the summer months at high temperatures. Some foams have experienced high temperature related sagging or running problems either at application or shortly thereafter.
It is accordingly desirable to improve the cohesiveness and high temperature stability of foams.
These and other objects are met by the foamable compositions of the instant invention. Compositions in accordance with the invention may be used, for example, to provide latex foam caulk and patching compounds, latex foam stucco including inside and outside wall treatment, ceiling and roof coatings, and latex foam adhesives. The compositions may be disposed in pressurized aerosol containers for foamed caulk bead application or they may be contained within large pressurized bulkpacks having flexible hose or gun connectors associated therewith so that building contractors and the like may be readily supplied with larger quantities of the compositions.
A composition in accordance with the invention comprises an aqueous latex emulsion of a film forming polymer. The latex emulsion is water dispersible and accordingly may be washed off a user""s hands by soap and water.
The composition further comprises microfibers. Preferably, both the film forming polymer and the microfibers have functional groups capable of forming bonds, particularly hydrogen bonds, between themselves to improve the cohesion of the resulting foam. Desirable cohesion properties have been obtained using film forming polymers having hydroxyl or carbonyl functionality with fibers having amine functionality. Most preferably, the microfibers are composed of linear polymers such as nylon to minimize steric hindrance.
The composition further comprises a lipophilic surfactant. Preferably, it comprises a solid, lipophilic non-ionic surfactant having an HLB value of about 3 to about 8, more preferably about 3.5 to about 6. These surfactants are water insoluble and are chosen from the group of fatty acid (i.e., C12 and greater) esters, fatty alcohol ethers and fatty acid amides. Most preferably, the surfactant comprises one or more ethoxylated fatty alcohols.
A host of liquidable gaseous propellant components may be employed. It is preferred to use a combination of dimethyl ether (DME) and a volatile liquid hydrocarbon wherein the liquid hydrocarbon is present, by volume, in an amount greater than the DME.
Without wishing to be bound to any particular theory of operation, it is thought that the solid lipophilic surfactant coats the volatile liquid hydrocarbon propellant constituent as the foamable composition is expelled from the pressurized container. The surfactant, on foam dispensing, changes from the liquid phase into the solid phase where it is positioned along the water/organic interface. At that location, the surfactant functions as a foam builder, supporting the bubbles formed by the volatile hydrocarbon and the surrounding polymer emulsion. On evaporation of the propellant and water from the emulsion, the polymer bubbles are stabilized by the waxy surfactant and polymer solids.
The high temperature stability of the composition may be improved by adding a stabilizer having a melting point greater than about 110xc2x0 F. Preferred foam stabilizers include polar, linear saturated long chain fatty alcohols having greater than about 20 C atoms in the molecule. Behenyl alcohol is most preferred.
Conventional fillers may also be added to the composition to provide anti-sagging properties or desired pigmentation.
Foams produced by the foamable compositions of the invention exhibit better cohesion (e.g., greater tensile strength) than prior art foams formed from prior compositions. This improved cohesion manifests itself in reduced brittleness and improved puncture resistance. Furthermore, the added strength decreases the likelihood of xe2x80x9cblow outxe2x80x9dxe2x80x94that is, a rupture of the surface skin and continued expansion of the foam through the rupture. This phenomenon compromises the water resistance of the foam (i.e. the surface deposition of the quaternary amine, Mackernium SDC-85).
The invention will be further described in conjunction with the appended drawings and detailed description.